<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="utf-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta
      name="viewport"
      content="width=device-width, initial-scale=1, maximum-scale=1, minimum-scale=1, user-scalable=no"
    />
    <meta name="description" content="Fog post process" />
    <meta
      name="cesium-sandcastle-labels"
      content="Showcases, Post Processing"
    />
    <title>Cesium Demo</title>
    <script type="text/javascript" src="../Sandcastle-header.js"></script>
    <script type="text/javascript" src="../CesiumUnminified/Cesium.js"></script>
  </head>
  <body
    class="sandcastle-loading"
    data-sandcastle-bucket="bucket-requirejs.html"
  >
    <style>
      @import url(../templates/bucket.css);
    </style>
    <div id="cesiumContainer" class="fullSize"></div>
    <div id="loadingOverlay"><h1>Loading...</h1></div>
    <div id="toolbar"></div>
    <script id="cesium_sandcastle_script">
      function startup(Cesium) {
        "use strict";
        //Sandcastle_Begin
        var viewer = new Cesium.Viewer("cesiumContainer", {
          shouldAnimate: true,
        });

        if (!viewer.scene.context.depthTexture) {
          window.alert("This browser does not support the fog post process.");
        }

        var tileset = new Cesium.Cesium3DTileset({
          url: Cesium.IonResource.fromAssetId(40866),
        });

        viewer.scene.primitives.add(tileset);

        viewer.scene.camera.setView({
          destination: new Cesium.Cartesian3(
            1216356.033078094,
            -4736402.278325668,
            4081270.375520902
          ),
          orientation: new Cesium.HeadingPitchRoll(
            0.08033365594766728,
            -0.29519015695063455,
            0.00027759141518046704
          ),
          endTransform: Cesium.Matrix4.IDENTITY,
        });

        var fragmentShaderSource =
          "float getDistance(sampler2D depthTexture, vec2 texCoords) \n" +
          "{ \n" +
          "    float depth = czm_unpackDepth(texture2D(depthTexture, texCoords)); \n" +
          "    if (depth == 0.0) { \n" +
          "        return czm_infinity; \n" +
          "    } \n" +
          "    vec4 eyeCoordinate = czm_windowToEyeCoordinates(gl_FragCoord.xy, depth); \n" +
          "    return -eyeCoordinate.z / eyeCoordinate.w; \n" +
          "} \n" +
          "float interpolateByDistance(vec4 nearFarScalar, float distance) \n" +
          "{ \n" +
          "    float startDistance = nearFarScalar.x; \n" +
          "    float startValue = nearFarScalar.y; \n" +
          "    float endDistance = nearFarScalar.z; \n" +
          "    float endValue = nearFarScalar.w; \n" +
          "    float t = clamp((distance - startDistance) / (endDistance - startDistance), 0.0, 1.0); \n" +
          "    return mix(startValue, endValue, t); \n" +
          "} \n" +
          "vec4 alphaBlend(vec4 sourceColor, vec4 destinationColor) \n" +
          "{ \n" +
          "    return sourceColor * vec4(sourceColor.aaa, 1.0) + destinationColor * (1.0 - sourceColor.a); \n" +
          "} \n" +
          "uniform sampler2D colorTexture; \n" +
          "uniform sampler2D depthTexture; \n" +
          "uniform vec4 fogByDistance; \n" +
          "uniform vec4 fogColor; \n" +
          "varying vec2 v_textureCoordinates; \n" +
          "void main(void) \n" +
          "{ \n" +
          "    float distance = getDistance(depthTexture, v_textureCoordinates); \n" +
          "    vec4 sceneColor = texture2D(colorTexture, v_textureCoordinates); \n" +
          "    float blendAmount = interpolateByDistance(fogByDistance, distance); \n" +
          "    vec4 finalFogColor = vec4(fogColor.rgb, fogColor.a * blendAmount); \n" +
          "    gl_FragColor = alphaBlend(finalFogColor, sceneColor); \n" +
          "} \n";

        var ellipsoid = viewer.scene.globe.ellipsoid;
        var postProcessStage = viewer.scene.postProcessStages.add(
          new Cesium.PostProcessStage({
            fragmentShader: fragmentShaderSource,
            uniforms: {
              fogByDistance: new Cesium.Cartesian4(10, 0.0, 200, 1.0),
              fogColor: Cesium.Color.BLACK,
            },
          })
        ); //Sandcastle_End
        Sandcastle.finishedLoading();
      }
      if (typeof Cesium !== "undefined") {
        window.startupCalled = true;
        startup(Cesium);
      }
    </script>
  </body>
</html>
